The analyzing power $A_y\left(\theta \right)$ for scattering of neutrons from deuterons at 10 MeV for 30° to 145° (c.m.) was measured to an accuracy better than ± 0.005. The results are compared to published $p-d$ data at 10 MeV, and convincing differences are noted for the first time. These differences provide a sensitive test both of calculations for the three-nucleon system and, more importantly, of the fundamental nucleon-nucleon interaction.

• Received 14 June 1982

DOI:https://doi.org/10.1103/PhysRevLett.49.312